Populations and Growth

KEY CONCEPT Populations grow in predictable patterns.

Population Dispersion

Survivorship Curves Type I Few offspring Low infant mortality Parental care of young Most survive until old age Large mammals, including humans

Survivorship Curves Type II Equal chance of living or dying throughout the lifetime Birds, reptiles, small mammals

Survivorship Curves Type III High infant mortality rate Many offspring No parental care Invertebrates, fish, amphibians, and plants

Changes in Population Size Growth factors Immigration: individuals moving into a population Births Shrinking factors Emigration: individuals moving out of a population Deaths

Changes in a population’s size are determined by immigration, births, emigration, and deaths. The size of a population is always changing. Four factors affect the size of a population. immigration births emigration deaths

Population growth is based on available resources. Exponential growth is a rapid population increase due to an abundance of resources.

Exponential Growth Early phase of growth High availability of resources Little competition Little predation

Logistic growth is due to a population facing limited resources.

Logistic Growth Limits on growth appear Competition for resources Predation Parasitism Illness

Carrying capacity is the maximum number of individuals in a population that the environment can support. A population crash is a dramatic decline in the size of a population over a short period of time.

Ecological factors limit population growth. A limiting factor is something that keeps the size of a population down. Density-dependent limiting factors are affected by the number of individuals in a given area.

Density-dependent limiting factors are affected by the number of individuals in a given area. predation competition parasitism and disease

Density-independent limiting factors limit a population’s growth regardless of the density. unusual weather natural disasters human activities

Human Population Growth Are humans in exponential or logistic growth?

U.S. Population Density - 2000 People per square mile 0-1 (white) 10-24 (green) 100-249 (blue) 1-4 (yellow) 25-49 (teal) 250-66,995 (dark blue) 5-9 (yellow-green) 50-99 (dark teal)